Ampeg BA115HP speaker popping

[goldtop5]

I have an Ampeg BA115HP bass combo amp that makes a popping noise whenever the amp is turned on or off. There is no DC voltage detected on the speaker terminal output. It will pass a signal to an 8 ohm speaker, but when I attach the stock speaker or anything else that's a 4 ohm load, it will see it as a short and the limiter bulbs would light up. Any suggestions?

[J M Fahey]

1) popping is a fact of life.
Some take an extra pain to damp or kill it, some don't care.
Annoying but no big deal.

2)

it will see it as a short and the limiter bulbs would light up

Not "a short" but "a load".
It will suck power (that's its job) , more current will pass, and bulb will shine brighter (that's its job) .

If amp works fine, plug it straight into the wall without the bulb limiter.

[Enzo]

Zillions of amps pop when the power switch is flipped. I don't consider it a problem.


What wattage bulb are you using?

[Leo_Gnardo]

I have an Ampeg BA115HP bass combo amp that makes a popping noise whenever the amp is turned on or off.

Rare the solid state amp that does not deliver a pop to the speaker on powering up or down. Those that don't often have a speaker relay that keeps amp disconnected from speaker until a short warmup period has passed, also disconnect the speaker immediately on removal of AC power. Those big ol' BGW amps come to mind.

[goldtop5]

When the amp came in for repair, the first thing it did was made a humming noise and the speaker pushed outward (and held that position) when the amp is turned on. I was throwing parts at it to see if the problem would go away. Eventually it did. But the popping noise still remained. I've read somewhere that these particular amps do that by nature. But the amp plays great now. It even pops when you hit the mute switch. I guess the customer will just have to live with that.

[goldtop5]

I'm using a current limiter that switches from a 40w to 300w bulb.

[The Dude]

This is more of an FYI than troubleshooting assistance. I have had several of this model in the shop with bad filter caps. If I recall correctly 5600UF ?- the ones on the high voltage rails, whatever they are. I'm not saying it's a "common" problem, but considering that these are recent production models (in cap years), more cap problems than you would expect. I wonder if you have one of these starting to fail causing your +&- rails to come up unevenly. The hint is your statement, "When the amp came in for repair, the first thing it did was made a humming noise and the speaker pushed outward (and held that position) when the amp is turned on.". If you have a cap tester, it might be worth checking those caps.

[drewl]

I have another in with cold bias which makes the tweeter sound blown.

Think I'll check those rails and caps then.

[Enzo]

A speaker pushed out means DC on the speaker. if you lose a filter cap, you also get loud hum, but the speaker doesn't stay at max.

If your cold bias makes distortion, it is probably crossover distortion, which you can find on a scope of the output.

[The Dude]

A speaker pushed out means DC on the speaker. if you lose a filter cap, you also get loud hum, but the speaker doesn't stay at max....

Agreed. However, if the rails come up at an uneven rate. There can be DC at the speaker until the failing cap charges and starts working. Of course there's also a large AC content. I guess technically the speaker wouldn't "stay" at max, but it can be there for quite some time depending on how close to dead the cap is.

[drewl]

Dammit I want to beat whoever designed the chassis/cabinet over the head with one of these!

A tight fit, now the cage nuts popped off and its a pain to pop the one behind the power trans back in.

If I have to remove the PT to pop it in I'm gonna kill something

[The Dude]

Obvious to some- not so much to others. So, excuse me for saying what some might consider obvious and stupid.
When you put in those cage nuts, put the tabs perpendicular to the direction the chassis slides in and out. If you put them parallel, sliding the chassis into the cabinet is more likely to pop them loose.

[drewl]

Obviously not obvious to the installers but something I always do when I have to put them back in.

[52 Bill]

The problem I find with those is that the chassis is so thin that when the mounting screws are tightened they deform the chassis, pulling the insert nuts out and in the line of the cabinet vinyl.

What I try and do is after the screw has been removed, use a thin straight blade screw driver to try and bent the metal back into place so that the chassis can be pulled out easier. And before reinstalling the chassis, I straighten out the chassis to make it easier to slide it back into the cabinet.

[drewl]

Yeah, that helps as the chassis definitely bends.